Fix argmin and argmax (#98)

* Fix argmin and argmax

* Revert bqd fix

* Add two small tests

* Moar tests to figure out what's wrong

* Fix tests

* Fix comparison order

* last fix

* One comp only

src/chainedvector.jl

@@ -825,8 +825,9 @@ function findXwithfirst(comp, f, x, y, i)
     for A in x.arrays
         for y′ in A
             y′′ = f(y′)
-            y = ifelse(comp(y′′, y), y′′, y)
-            i = ifelse(comp(y′′, y), i′, i)
+            c = comp(y′′, y)  # store this before y changes
+            y = ifelse(c, y′′, y)
+            i = ifelse(c, i′, i)
             i′ += 1
         end
     end
@@ -835,8 +836,8 @@ end
 
 Base.findmax(x::ChainedVector) = findmax(identity, x)
 Base.findmin(x::ChainedVector) = findmin(identity, x)
-Base.argmax(x::ChainedVector) = findmax(identity, x)[1]
-Base.argmin(x::ChainedVector) = findmin(identity, x)[1]
+Base.argmax(x::ChainedVector) = findmax(identity, x)[2]
+Base.argmin(x::ChainedVector) = findmin(identity, x)[2]
 Base.argmax(f::F, x::ChainedVector) where {F} = x[findmax(f, x)[2]]
 Base.argmin(f::F, x::ChainedVector) where {F} = x[findmin(f, x)[2]]
 

test/chainedvector.jl

@@ -284,6 +284,17 @@
     @test all(==(2), x)
     @test length(x) == 5
 
+    # https://github.com/JuliaData/SentinelArrays.jl/issues/97
+    x = ChainedVector([[18, 70, 92, 15, 65], [25, 14, 95, 54, 57]])
+    @test findmax(x) == (95, 8)
+    @test findmin(x) == (14, 7)
+    @test argmax(x) == 8
+    @test argmin(x) == 7
+    @test findmax(inv, x) == (inv(14), 7)
+    @test findmin(inv, x) == (inv(95), 8)
+    @test argmax(inv, x) == 14
+    @test argmin(inv, x) == 95
+
     x = ChainedVector(Vector{Float64}[])
     @test !any(x -> iseven(x), x)
     @test !any(map(x -> iseven(x), x))